Conventionally, serum diagnosis of identifying a tumor marker in blood serum, tissue diagnosis by biopsy, and cytodiagnosis have been known as cancer diagnoses. However, these methods are poor in reliability and give variation in diagnosis resulting from individual assessments or different assessment methods in medical institutes. In recent years, molecular diagnosis based on a gene or protein expressed in living bodies is examined as a standardized cancer diagnostic method with less variation in diagnosis by diagnosticians. As molecular diagnosis based on protein, various methods using a cyclin dependent kinase (also referred to hereinafter as “CDK”) have been proposed.
For example, US 2007/231837 describes a method of judging the properties of cells or malignancy of cancers by comparing the CDK specific activity ratio obtained from the activity value/expression level ratio between two CDKs. According to this method, a risk of cancer recurrence can be predicted based on the CDK specific activity ratio between two CDKs from a cancer patient to be examined.